You should be able to have as many "Poser" folders as you want under D|S - you'll get a separate entry for each in the Content palette. I have half-a-dozen or so, mostly on my second HD, with D|S itself on my main drive. It may be that D|S scraps the unavailable folders if you start with the removable drive disconnected, or that it is failing to keep track of the removable drive at all for some reason, but it certainly sounds as if you've found a bug of some sort.